Laminating processes and laminating apparatuses of this type are known, for example, from WO96/25902 and WO99/28048. Whereas WO96/25902 provides for the continuous film of an adhesive composition to be applied to a first substrate without contact between said substrate and the application device, after which a second substrate is placed on the continuous adhesive composition film, and then this three-layer composite is guided through a compression gap between two rollers that are pressed against one another, in order to force any air out from between the two substrates and the adhesive film, WO99/28048 provides for the adhesive film to be applied to a first web-type substrate and then pressed onto the substrate by guiding the web-type substrate, along with the continuous adhesive film, through a compression gap between two rollers pressed against one another. The second substrate is applied to the adhesive coated side only after the above step, and is pressed on in another compression gap formed by two pressure rollers. While it is desirable in the process known from these two publications to apply the continuous adhesive composition film to the first substrate without contact between the coating appliance and the substrate or a roller, other processes described in these two publications are implemented with contact, for example using an oscillating or application roller or other direct contact method, for example with direct contact between a slot nozzle and the first substrate.
Using a compression roller gap to press the continuous adhesive composition film onto one or both of the substrates results in an uneven distribution of the adhesive film over the at least one substrate, because the substrate is at least microscopically irregular, and in some cases is also macroscopically irregular, on its surface to be laminated. In the compression gap, a film of uneven thickness is formed from the initially substantially uniform adhesive composition film, in that the freely flowing constituents of the adhesive composition accumulate in “troughs” in the substrate surface, whereas adhesive is forced away from the protruding “peaks” or “ridges” in the surface structure of the substrate toward the “troughs.” This adversely affects the adhesive capacity of the laminate and/or other properties, such as the clarity of the transparency of a transparent laminate substrate.
The contactless application process, so-called “curtain coating,” involves another problem with the uniformity of application thickness along the lateral edges of the adhesive composition film, because the film contracts from its lateral edges toward the center (so-called “neck in”) as it travels from the slot nozzle to the substrate. As a result, a line of significantly thicker coating becomes deposited on the substrate along the application edges of the film. This is unacceptable when the web-type substrate is wound onto a reel—even if the difference in thickness as compared with the web center is only slight. These thicker edges must be cut away by cutting the web lengthwise, and must be discarded as waste. Thus in this case, both substrate material and adhesive composition are irretrievably lost.